The present invention relates to an aircraft gas turbine engine.
In operation aircraft gas turbine engines encounter many different weather conditions. Heavy ingestion of rain, or hail, into a gas turbine engine during flight at low engine power settings may result in a compressor surge and an in-flight shut down. In order to avoid this problem the gas turbine engine is operated at a sufficiently high power level and/or is provided with sufficient compressor bleed to provide an adequate compressor surge margin.
Ingestion of water into a gas turbine engine during flight at high power settings may result in sudden cooling of the compressor blades while the compressor blades are driven at high rotational speeds. To counteract this problem thicker compressor blades have been used, which affects the aerodynamic efficiency of the compressor blades.
Ingestion of ice crystals into a gas turbine engine during flight at high altitudes may result in ice accretion on components of the gas turbine engine and shedding of ice into the core of the gas turbine engine. The ice shedding may cause damage to compressor blades and compressor vanes and/or may cause compressor surge and/or flame out in the combustor of the gas turbine engine. To counteract this problem the idle speed of the gas turbine engine is increased by the aircraft pilot and/or thicker compressor blades have been used in case the idle speed is not increased, which affects the aerodynamic efficiency of the compressor blades.
Therefore, the prior art manually adjusts the operation of the gas turbine engine away from optimum aerodynamic performance in order to protect the gas turbine engine from damage and/or changes the design of the components to increase the damage tolerance, increases the thickness, of the components, compressor blades, but moves away from optimum aerodynamic performance.
It is known to provide ice detectors on aircraft which indicate that the conditions are such that ice may form on cold aircraft components, e.g. wings, fuselage, pylon, and gas turbine engine components, e.g. intake, fan etc. The output signal of these sensors is used to initiate automatic aircraft anti-icing and/or engine anti-icing or activate a warning signal inside an aircraft cockpit such that the pilot initiates aircraft anti-icing and/or engine anti-icing. It is also known to use temperature sensors and altitude sensors to detect conditions which may form ice.